In my U.S. Pat. No. 3,759,141, issued Sept. 18, 1973, I disclose a steam engine which has a number of highly desirable features including provisions for the double use of steam and including valve arrangements selectively operable to obtain double use of the steam with movement of the piston in both directions, as desired. The design as disclosed in my patent is, however, more complicated than would be desirable, especially for use in driving automobiles and other vehicles. It also is of relatively large size and is not as compact as would be desirable.